Adding two numbers in unix

Question

I tried to add two numbers by below logic:

num=0001
newnum=`expr $num + 1`
echo $newnum

But it returns '2', my desired output is '0002'.

num=0001
newnum=`expr $num + 0001`
echo $newnum

I used above logic also,but no use. What is needed here to get my desired output.
Thanks in advance.

Which shell are you using? (type 'echo $SHELL' to find out). Also, look at the "printf" command. — rojomoke
– rojomoke, Commented Jan 3, 2014 at 9:32
What you wrote won't work -- you can't have a space after =. I don't know how you're getting 2 with that code. — Barmar
– Barmar, Commented Jan 3, 2014 at 9:33

Barmar · Accepted Answer · 2014-01-03 09:32:21Z

2

Use printf to print numbers with leading zeroes:

printf "%04d\n" $num

You shouldn't do arithmetic with numbers with leading zeroes, because many applications treat an initial zero as meaning that the number is octal, not decimal.

answered Jan 3, 2014 at 9:32

Barmar

789k57 gold badges554 silver badges669 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Naveen Reddy CH Over a year ago

It is working..Thanks for your quick reply. This is the simple and good one!

devnull · Accepted Answer · 2014-01-03 09:32:07Z

1

Use printf:

$ num=0001
$ printf "%04d" $(expr $num + 1)
0002

In order to assign the result to a variable, say:

$ newnum=$(printf "%04d" $(expr $num + 1))
$ echo $newnum
0002

answered Jan 3, 2014 at 9:32

devnull

124k33 gold badges247 silver badges234 bronze badges

Comments

dogbane · Accepted Answer · 2014-01-03 10:04:40Z

0

Numbers with leading zeros are interpreted as octal numbers. In order to treat them as decimals you need to prepend 10# to the number. Finally, use printf to pad the number with zeros.

num=0001
newNum=$((10#$num + 1))
paddedNum=$(printf %04d $newNum)

answered Jan 3, 2014 at 10:04

dogbane

276k77 gold badges407 silver badges415 bronze badges

Collectives™ on Stack Overflow

Adding two numbers in unix

3 Answers 3

1 Comment

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

1 Comment

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related